ARTYKUŁY NAUKOWE Rekonstrukcja kierunków ruchu lodu w obrębie lobu górnej Odry
Abstract
Reconstruction of the ice-flow directions within the Upper Odra Lobe (S Poland).
A b s t r a c t. The Upper Odra Lobe – the southernmost part of the Scandinavian ice sheet during the Odranian (Drenthe) glaciation – was formed in the area of the Niemodlin Plain and the western part of the Racibórz Basin. It created a complex structure consisting of several sublobes: Odra, Nysa, Ruda and Kłodnica sublobes. The study focused on the basal till deposited during ice sheet advance. Ice flow directions and the general pattern of ice mass distribution in the Upper Odra Lobe were defined based on the clast fabric. The resulting distribution of ice-flow palaeodirections suggest that the Upper Odra Lobe was formed by the mass of ice moving divergently from the Opole Plain located to the north of the Racibórz Basin. Ice-flow lines coincide with the pattern of major geomorphological units. The most intensive movement of the ice took place in the depression of the central part of the Silesian Lowland. From there, in the vicinity of the Niemodlin Plain, the ice sheet moved in different directions, forming smaller sublobes in several valleys. Strong relationship between the ice flow directions and morphology confirms the idea of a smaller ice sheet extent in the Racibórz Basin and Moravian Gate. Highly concentrated flow of ice in the back-lobe area,
interpreted in this study, suggests that the lobe development resulted not only from the ice sheet adapting to the basement relief, but was also conditioned by a spatially varying distribution of ice, i.e. increased ice supply to the Niemodlin Plain and the western part of the Racibórz Basin.
A b s t r a c t. The Upper Odra Lobe – the southernmost part of the Scandinavian ice sheet during the Odranian (Drenthe) glaciation – was formed in the area of the Niemodlin Plain and the western part of the Racibórz Basin. It created a complex structure consisting of several sublobes: Odra, Nysa, Ruda and Kłodnica sublobes. The study focused on the basal till deposited during ice sheet advance. Ice flow directions and the general pattern of ice mass distribution in the Upper Odra Lobe were defined based on the clast fabric. The resulting distribution of ice-flow palaeodirections suggest that the Upper Odra Lobe was formed by the mass of ice moving divergently from the Opole Plain located to the north of the Racibórz Basin. Ice-flow lines coincide with the pattern of major geomorphological units. The most intensive movement of the ice took place in the depression of the central part of the Silesian Lowland. From there, in the vicinity of the Niemodlin Plain, the ice sheet moved in different directions, forming smaller sublobes in several valleys. Strong relationship between the ice flow directions and morphology confirms the idea of a smaller ice sheet extent in the Racibórz Basin and Moravian Gate. Highly concentrated flow of ice in the back-lobe area,
interpreted in this study, suggests that the lobe development resulted not only from the ice sheet adapting to the basement relief, but was also conditioned by a spatially varying distribution of ice, i.e. increased ice supply to the Niemodlin Plain and the western part of the Racibórz Basin.